1. Field of the Invention
The present invention relates to an endoscopic high-frequency treatment tool which is inserted into a treatment tool insertion channel of an endoscope.
2. Description of the Related Art
A typical endoscopic high-frequency treatment tool is constructed and arranged so that a conductive wire is inserted into an insulating flexible sheath, which is inserted into a treatment tool insertion channel of an endoscope, and so that a high-frequency cutting electrode exposed at the outer surface of the flexible sheath in the vicinity of the end thereof and the conductive wire are connected together in the flexible sheath.
However, an operation connecting the conductive wire that is inserted into the flexible sheath and the high-frequency cutting electrode to each other needs to be performed with a high degree of precision. If the connection between the conductive wire and the high-frequency cutting electrode is even a little poor, there is a possibility of the high-frequency cutting electrode falling into the body of a patient.
To prevent this problem from occurring, an endoscopic high-frequency treatment tool in which a stranded wire made of metal is used as a conductive wire and in which a part of the strands having the conductive wire is extended from the conductive wire to be used as a high-frequency cutting electrode is known in the art. This type of endoscopic high-frequency treatment tool is disclosed in Japanese patent gazette No. 57-811.
However, if a part of the strands of the conductive wire is extended from the conductive wire to be used as a high-frequency cutting electrode, the end of the conductive wire which corresponds to the base (root) of the high-frequency cutting electrode may become frayed and thus expand radially to thereby cause a malfunction. This problem tends to occur especially in the case where the conductive wire is operated to rotate about its axis in the flexible sheath.
FIG. 7 of the aforementioned Japanese patent gazette shows an embodiment of an endoscopic high-frequency treatment tool in which a high-frequency cutting electrode formed by a part of the strands of a conductive wire is looped to extend backward and then joined at the end of the high-frequency cutting electrode to the end surface of the conductive wire. However, such a structure cannot securely prevent the conductive wire that is made of strands from becoming frayed when the conductive wire is repeatedly rotated about its axis. Moreover, if the end of the high-frequency cutting electrode is soldered to the end surface of the conductive wire, the subsequent flux-residue cleaning operation becomes extremely troublesome. Furthermore, if the end of the high-frequency cutting electrode is brazed to the end surface of the conductive wire, the application of heat during brazing weakens the base of the high-frequency cutting electrode, and therefore may cause the high-frequency cutting electrode to be damaged during use.